Abstract

Evolutionary experimentation (Bullock 1984) has given rise to a large repertoire of locomotor, and other, behaviors in malacostracan crustaceans. Just within the Decapoda (Fig.1), behavioral diversity exceeds the considerable morphological diversity. More than half a century of research on the neurobiology of decapods has led to the insight that neurobehavioural circuits are often fractionated into subsets of neurons (e.g.,central pattern generators: Ikeda and Wiersma 1964; Mendelson 1971; Skorupski et al. 1984; Sillar et al. 1987; Murchison et al. 1993; groups of motor units operating muscles at single joints or even single muscles: Ayers and Clarac 1978) which are responsible for discrete aspects of behavior and that separate mechanisms exist to link the activities of these units. These latter coordinating mechanisms, which include coordinating interneurons (Wiersma and Ikeda 1964; Stein 1971; Namba and Mulloney 1999; Mulloney, this Vol.) and neuromodulatory neurons (Bartos et al. 1999; Blitz et al. 1999; Marder this vol), provide much of the adaptive flexibility of motor behavior as a whole. This organization suggests that evolutionary flexibility of motor systems might also be greatest in the coordinating mechanisms linking subsets of neurons or motor modules which themselves are more evolutionarily conserved. We summarize evidence from decapod locomotion for this hypothesis, then briefly address evolution of motor modules themselves.

Namba H, Mulloney B (1999) Coordination of limb movements: three types of intersegmental interneurons in the swimmeret system and their responses to changes in excitation. J Neurophysiol 81: 2437–2450PubMedGoogle Scholar